The manufacture of thin-layer solar cells with varied structure is already known. They can be deposited on rigid carriers such as glass, but also onto foils, i.e. thin, flexible metallic or polymeric carriers. The basic structure of a thin-layer solar cell is depicted in FIG. 1 using a CIGS thin-layer solar cell on a foil base and includes the carrier or substrate which for example consists of a foil (1), the back contact layer (2), which in essence comprises a molybdenum layer in the example, the absorber layer made for example of CIGS (3), a buffer layer made for example of cadmium sulfide (4), a tunnel contact made for example of intrinsic zinc oxide and the transparent front-side electrode, which consists of a transparent oxide conductor as for example indium tin oxide (ITO) or aluminum-doped zinc oxide. The tunnel contact and the front-side electrode (also designated as a transparent front contact layer) are jointly depicted as a layer (5). It is advantageous for manufacture of thin-layer solar cells to continuously run the process during layer deposition.
Achievement of serial connection of thin-layer solar cells in the form of a monolithic integration is also known. The procedures for this are found, for example, in U.S. Pat. No. 5,593,901. As described with the building up of thin-layer solar cells and their connection, for a monolithically integrated connection, alternating coating and surface-treatment steps must be carried out. Deposition of the individual layers of the thin-layer solar cell is thus interrupted by multiple surface-treatment steps.
To avoid an interruption of the deposition processes, it was suggested in WO 2008/157807 A2 to carry out all the surface-treatment steps after manufacture of the complete layer package, and to fill them with electrically conducting polymeric paste or electrically insulated polymeric paste (FIG. 2). FIG. 3 shows the process sequence based on prior art. The point of departure is the layer package depicted in FIG. 3 (a) of substrate (1), rear contact layer (2), photoactive layer (3), buffer layers (4) and transparent front contact layer (5). This layer package is now surface-treated, as shown in FIG. 3 (b), and subdivided into individual segments. Any number of individual segments can initially be chosen. For each individual segment, 3 surface-treatment steps are needed. The individual surface-treatment steps are explained in what follows with the aid of FIG. 3 (b). Surface treatment A completely splits up the transparent front contact layer (5), so that the buffer layers (4) and the absorber layer (3) become visible. Surface treatment B splits up all layers above the back contact layer (2) and thus reveals them. With surface treatment C, the complete layer package, including the back contact layer above the substrate is split up. To achieve a series connection between the individual segments defined by the surface treatment, a connection from the back contact layer of a segment to the front contact layer of a following segment must be achieved. As per the prior art, this connection is generated by means of an electrically conducting polymeric paste, which is filled into the surface-treated trench B (see FIG. 3 (d)). The surface treatment A serves to prevent a short circuit of the individual segments adjoining the front contact layers. Surface treatment C assumes this task, albeit for the individual segments adjoining the back contact layers. Surface treatments A and C are filled with an electrically insulating polymeric paste (see FIG. 3 (c)).
The known technical solutions have a number of drawbacks which can be subdivided into two aspects.